RE: [Springframework-developer] webflow: subflow behavior question

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As Erwin mentioned, there should be no concern of thread safety here.  Just
create a prototype instance that encapsulates the context you need an pass
it to the spawned subflow.  That'll be thread safe, as operations on flow
executions are synchronized per session per request.

"PersonSearchAlgorithm" will would be a callback to some kind of contextual,
query, yes?  Yea, to me it makes sense to parameterize the sub flow
execution with an instance of an appropriate contextual implementation of
that interface (e.g "all persons where manager != <x>, or all persons not
already attending or excluded"), delegating down to the DAO layer to
actually perform the data access.  I like the notion of this better than
passing in a snapshot array of persons to exclude.

HTH! Just curious, what is the web flow article? When will it be published?

Keith

Keith Donald
Interface21 - Spring Training, Consulting, and Support, "From the Source"
http://www.springframework.com

-----Original Message-----
From: spr...@li...
[mailto:spr...@li...] On Behalf Of
Erwin Vervaet
Sent: Monday, March 28, 2005 11:35 AM
To: spr...@li...
Subject: Re: [Springframework-developer] webflow: subflow behavior question

Threading issues are limited in web flows since a flow execution is 
basically single threaded: i.e. the flow execution entry methods (start() 
and signalEvent()) are synchronized. (At least this is the behaviour in the 
new implementation in the sandbox.)

Ofcourse you could also pass the list of ids to the Person subflow. In that 
case your "subflow signature" would be something like

public Person PersonFlow(String action, Person[] personsToExclude)

We're maintaining documentation related to the "new" Spring web flow system 
at http://opensource.atlassian.com/confluence/spring/display/WEBFLOW/Home. 
Keith Donald has been working on a new partical guide that you can find 
there.

Regarding the "old" Ervacon Spring web flow: I will let it go to 1.0.0 and 
then provide a migration guide to the new Spring web flow system. Ervacon 
Spring web flow is still useful for those people that stick with Spring 
1.1.x, but if you have 1.2 or later it's probably better to go with the new 
system.

Erwin

Erwin Vervaet
erw...@er...
----- Original Message ----- 
From: "Steven Devijver" <ste...@gm...>
To: <spr...@li...>
Sent: Monday, March 28, 2005 5:51 PM
Subject: Re: [Springframework-developer] webflow: subflow behavior question

> Hi Erwin,
>
> Although this is just a silly example to highlight my question passing
> behavior through the model does seem a bit awkward to me. Especially,
> the behavior class would also contain state (unless the state is
> passed separately in the model but then the Person flow would need to
> pass the state to the behavior). This would make the design not
> thread-safe.
>
> In this scenario I would prefer to pass a list of ID's of Persons that
> cannot be shown in the Person flow and implement the behavior once.
> I'm looking into this because I'm working on an article on webflow.
>
> btw, I found you article "Spring Web Flows: A Practical Guide" very
> helpful. Are you planning to keep it up to date with the latest
> changes to WebFlow (e.g. the changes to the action interface)?
>
> Thanks
>
> Steven
>
>
> On Mon, 28 Mar 2005 17:11:32 +0200, Erwin Vervaet
> <erw...@er...> wrote:
>> The Manager and Meeting flow indeed have to put a SearchAlgorithm 
>> instance
>> in flow scope, probably in an 'initFlow' action state or something like
>> that, which could also take care of any type of flow data initialisation,
>> e.g. pulling in reference data.. You then use an attribute mapper to pass
>> the SearchAlgorithm to the subflow in the subflow state.
>>
>> Erwin Vervaet
>> erw...@er...
>> ----- Original Message -----
>> From: "Steven Devijver" <ste...@gm...>
>> To: <spr...@li...>
>> Sent: Monday, March 28, 2005 4:59 PM
>> Subject: Re: [Springframework-developer] webflow: subflow behavior 
>> question
>>
>> > Hi Erwin,
>> >
>> >
>> >> I would probably do this by making the search (or filter) algorithm
>> >> configurable for the Person flow. That way the calling parent flow can
>> >> pass
>> >> in the algorithm to use. I find that a good way to think about a flow 
>> >> is
>> >> as
>> >> a method: it has input parameters and can return results. So your 
>> >> person
>> >> flow would be something like this, when expressed as a method:
>> >>
>> >> public Person PersonFlow(String action, SearchAlgorithm algorithm)
>> >>
>> > Does this mean the Manager and Meeting flows have to put a
>> > SearchAlgorithm instance in the session (or the model?) before passing
>> > control to the Person subflow? Does this require an action-state
>> > before the flow-state in the Manager and Meeting flows?
>> >
>> > Thanks
>> >
>> > Steven
>> >
>> >
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>
> -- 
> "If you want to be a different fish, you gotta jump out of the school."
> -- Captain Beefheart
>
>
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